1. Field of the Invention
This invention relates to an optical wavelength converting device, which is of the optical waveguide type, and more particularly to an optical wavelength converting device, which comprises an waveguide means constituted of a solid laser medium and a nonlinear optical material overlaid one upon the other. This invention also relates to a laser diode pumped solid laser, in which a solid laser medium is pumped by a semiconductor laser (or a laser diode), and more particularly to a laser diode pumped solid laser, wherein its solid laser medium has a function for converting a wavelength such that a laser beam, which has been obtained from solid laser oscillation, may be converted into its second harmonic, or the laser beam, which has been obtained from solid laser oscillation, and a different laser beam may be converted into a wave having a frequency equal to the sum of or the difference between the frequencies of the two laser beams.
2. Description of the Prior Art
Laser diode pumped solid lasers have been proposed in, for example, Japanese Unexamined Patent Publication No. 62(1987)-189783. The proposed laser diode pumped solid lasers comprise a solid laser rod, which has been doped with a rare earth metal, such as neodymium (Nd). The solid laser rod is pumped by a semiconductor laser.
In the laser diode pumped solid laser of this type, in order for a laser beam having as short a wavelength as possible to be obtained, a bulk single crystal of a nonlinear optical material for converting the wavelength of a laser beam, which has been produced by solid laser oscillation, is located in a resonator of the solid laser. The laser beam, which has been produced by the solid laser oscillation, is thereby converted into its second harmonic, or the like. An example of such a laser diode pumped solid laser having the function for converting a wavelength is disclosed in U.S. Pat. application Ser. No. 406,018.
As disclosed in U.S. patent application Ser. No. 406,018, in the laser diode pumped solid laser of the aforesaid type, for example, an organic material is utilized as the nonlinear optical material such that the efficiency, with which the wavelength conversion is effected, may be kept high. However, with the conventional laser diode pumped solid laser of the aforesaid type, the efficiency, with which the wavelength conversion is effected, cannot be kept sufficiently high. Thus there is a strong demand for laser diode pumped solid lasers which are capable of converting wavelengths of laser beams with a sufficiently high efficiency.
Also, the techniques for locating a bulk single crystal of a nonlinear optical material in a resonator of a solid laser have the drawback in that considerable time and labor are required to align the optical axis of a solid laser rod and the optical axis of the bulk single crystal with each other. Additionally, the solid laser rod and the bulk single crystal are formed as different independent parts, and therefore the solid laser cannot be kept small in size. Moreover, there is the risk that error occurs in aligning the optical axis of the solid laser rod and the optical axis of the bulk single crystal with each other. Therefore, the reliability and mode stability of the solid laser cannot be kept good.